I have a 5" HB color gps/2d (can't remember the model #) on the bow of my PT175, might as well plan on raising the HU up 12" or so, I had it mounted to the floor, and it works, but up 12" makes a world of difference. If you go with the Terrova, go ahead and get Ipilot as well, $$ WELL spent for maintaining your speed and making the day fishing MUCH MORE enjoyable and easier on you in terms of controlling the boat. GL on your upgrades.
GO BIG ORANGE !
I meant to behave, but there were just way too many other options available at the time.